Coil and core assembly for an electric tool or the like

ABSTRACT

An electric tool in which an elongate casing defines a handle portion for the tool with an interior cavity and an opening at one end leading to the cavity. An elongate electromagnet is mounted in the cavity and an armature is mounted in the casing adjacent the opening for vibratory movement relative to the electromagnet. An etching rod extends through the opening and is secured to the vibrating armature. A spring biased adjusting collar is threaded into the opening and exposed exteriorly of the casing for grasping to adjust the displacement of the etching rod. The core of the electromagnet comprises two pieces with a coil therebetween and hinged at adjacent end for pivotal movement toward and away from the coil. A hinge member for the two piece core guides the armature and also guides the etching rod.

I United States Patent 1 1 3,596,118

[72] inventor DhuAlne J. Davis [56] Rotor-cum Cited Wbenton, lll. UNITED STATES PATENTS P i 1970 694,778 3/1902 Perret 310/20 3,012,113 I2/l96l Koehler m1. 29/606 [45] Patented July 17, 197! 3 93 9 7 3,3 9,0 (ill 6 Beers 3l0/36X [73] Assrgnee llerrnetk Col Co. Inc.

2,719,356 l0/l955 R1tter.... 310/29 X Division of Ser. No. 669,870, Sept. 22, 1967.

3,263,l05 7/1966 Heyek 310/29 X which 3 072 809 l/l963 Jepson etal. 310/29 615.102. Feb. 10. I967. now Patent No. 3,375,380. dated Mar. 26, 1968, Primary Examiner-D. F. Duggan Attorney-Hofgren, Wegner, Allen, Stellman and McCord ABSTRACT: An electric tool in which an elongate casing defines a handle portion for the tool with an interior cavity and an opening at one end leading to the cavity. An elongate electromagnet is mounted in the cavity and an armature is [$4] COIL AND CURE ASSEMBLY FOR AN LE TRIC mounted in the casing adjacent the opening for vibratory TOOL ORTHE LIK movement relative to the clectromagnet. An etching rod ex 5 Chills, 4 Dnwllll 8 tends through the opening and is secured to the vibrating armature. A spring biased adjusting collar is threaded into the [52] [13. CL 310/17, opening and exposed exteriorly of the casing for grasping to 3l0/29, 29/606 adjust the displacement of the etching rod. The core of the [S 1] Int. Cl 02k 33/00 electromagnet comprises two pieces with a coil therebetween [50] FleldolSea-d: 3l0/2l, 22, and hinged at adjacent end for pivotal movement toward and 25,29,152. 15. 2l62l8.42. l7.33.2 0.3630. 30/431335/2982336/l32. 2l6. 22 l 29/606 away from the coil. A hinge member for the two piece core guides the armature and also guides the etching rod.

PATENTEU JUL27 I97l FIGZ FIG3

/ INVENTOR DUHAINE JDAVIS 4%, JJMZZZWJWJATTORNEYS COIL AND CORE ASSEMBLY FOR AN ELECTRIC TOOL OR THE LIKE BACKGROUND OF THE INVENTION This application is a division of applicant's copending application, Ser. No. 669,870, filed Sept. 22, I967, which, in turn, is a division of applicant's application, Ser. No. 615,102, filed Feb. 10, 1967, now US. Pat. No. 3,375,380, issued Mar. 26, 1968. Electric etching tools generally include an electromagnetic motor mounted within a casing and having a core and coil and a movable armature which oscillates an etching rod for the purpose of marking or engraving on hard surfaces such as metal or plastic. The etching tools heretofore available include a relatively large and bulky casing within which the electromagnet is mounted. This bulkiness results from employing a standard, somewhat rectangularly shaped, coil and core. Such structures are cumbersome and difficult to handle and use. They in no way resemble the elongate writing instruments with which most people are familiar. Furthermore, the operating mechanism within the tools casing is made of numerous relatively detailed pans and thus the tool is much too expensive for general use.

SUMMARY OF THE INVENTION One object of this invention is the provision ofa novel elongate etching tool having a coil, core and armature structure so constructed that the etching tool as a whole simulates a pencil or other elongate writing instrument.

Another feature of the invention is the provision of an etching tool of the character described which includes a readily accessible means for adjusting the mechanical displacement of the etching rod.

Still another feature is the provision of a single nose piece within the casing to guide the etching rod, to guide the armature member and prevent it from binding, and to position the spring means which biases the armature away from the electromagnet.

It is yet a further object of this invention to provide a tool which includes a two piece hinged core which permits easy manufacture and assembly ofthe tool.

Still a further feature is the provision of such a tool having an elongated coil and core configuration with an armature at one end of the core, permitting the tool to be formed with a very slender shape.

Other features and objects of this invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an etching tool embodying the invention;

FIG. 2 is a plan view of the tool with a portion of the casing removed;

FIG. 3 is a sectional view taken generally along the line 3-3 of FIG. I; and

FIG. 4 is an exploded view of the etching tool showing the component parts thereof.

DETAILED DESCRIPTION Turning now to the drawings, an etching tool embodying the invention has a casting C which houses the component parts of the tool and which is comprised of two matching casing halves l and 11. An electromagnetic motor, generally designated I4, is positioned in a cavity (FIG. 4) within the casing. The casing has an opening 16 in one end thereof and through which an etching rod 18 extends. Terminal leads 20 extend through the casing from the electromagnetic motor at a point remote from the etching rod, preferably at the opposite end of the tool. As can be seen from the drawings, the casing is elongate and has wall means which define a slender tool simulating a pencil or other writing instrument and which is easily handled by the user. The front portion 22 of the casing tapers toward opening I6 to facilitate easy grasping and manipulation by the user. The etching rod 18 has a pointed tip 24, preferably of carbide or other hard material, and is oscillated by the electromagnetic motor to permit markings to be etched by the tip on a hard surface such as metal or plastic. The casing is constructed so that the electromagnet is disposed within the cavity is beneath a grasping portion 25 (FIG. 1) of the casing.

The AC electromagnetic motor 14 includes an elongate oval coil 26, a two piece core comprised of two like, elongate, generally rectangular members 28 pivotally secured together at adjacent ends 280 by a combination nose piece and hinge member 30, and an armature member 32. The motor is mounted in the casing with the armature at the forward end of cavity 15 for vibratory movement toward and away from the elongate electromagnet in the direction of arrow A (FIG. 4). The core members each have a pole face 33 at its forward end. The coil and core of the electromagnet are elongated in the same direction as the casing C. The etching rod 18 is fixed to the armature member 32. A coil spring 34 embraces the inner end of the etching rod within the casing and is disposed between the nose piece 30 and the armature 32 to bias the armature 32 and etching rod 18 away from the core of the electromagnet. As the current alternates in the coil of the electromagnet, the armature and etching rod oscillate against spring 32 toward and away from pole faces 33. The armature 32 being at the forward end of the cavity rather than within the coil and/or core permits the casing to be slender, simulating a pencil.

The nose piece 30 performs four functions in the embodiment of the tool illustrated in the drawings. Its parallel walls 36 serve to guide the armature member 32 and prevent its twisting or binding during oscillation toward and away from the core. The nose piece is provided with a bushing 38 which performs the dual role of maintaining the position of coil spring 34 while guiding the etching rod 18 in its oscillation toward and away from the electromagnetic core. In addition, the single nose piece provides the hinge means for the two piece core to provide for easy assembly of the electromagnet, as hereinafter described.

A means is provided for adjusting the mechanical displacement of the etching rod 18 and includes a coil spring 40 embracing the etching rod 18 within the casing forwardly of the armature member 32. A portion of the opening I6 is threaded to receive a threaded adjusting collar 42 which bears against the outer end of coil spring 40 within the casing by means of a washer 43. A portion of the collar 42 at its outer end is exposed exteriorly of the casing for grasping and turning by the user to adjust the compression of coil springs 40 and 34. The amount of compression of spring 40 governs the outer limit of movement of armature 32 and etching rod I8 as they are biased outwardly by spring 34. Thus a simple means at the forward end of the tool is available for adjusting the displacement of the etching rod and thus the depth of the etching on the hard surface.

A ring 44 is threaded onto the front of the tapered casing portion 22 to secure the front of the casing halves together. A boss 45 is formed integrally with the rear of the casing half 10 within cavity 15 and frictionally fits into a socket 46 on the casing half 11 within cavity 15 to secure the rear of the casing halves together.

Referring to FIG. 3, each elongate core piece 28 is a stack of laminations', and the elongate coil 26 is disposed between the two core pieces. The stacks of laminations include wider central laminations 44 which extend into the aperture of coil 26. In the embodiment illustrated, both core pieces 28 include wider central laminations 47 which extend half way through the coil 26. The core may be formed with only one core piece 28 having wider central laminations which extend all the way through the coil. The cross-sectional area of the central laminations are of the same order as the area of the pole faces 33. The ease of assembly of this construction is readily apparent. The laminated core pieces 28 and nose piece or hinge member 30 may easily be assembled independently of coil 26. Then, by spreading the two core pieces apart, the coil may be positioned therebetween and the core pieces closed on the coil. The core and coil assembly as seen best in FIG. 2, fits into the casing cavity whereby the assembly does not employ screw or other fastening means to hold it together or to mount it in the casing. The single nose piece 30 positions coil spring 34, guides etching rod 18 and prevents armature member 32 from binding. Since the adjusting collar 42 is threaded directly into the casing C, the entire structure is assembled into the casing without a single screw or fastening means. Once the component parts are assembled in the casing, the only fastening means necessary is to secure the two casing halves l0 and ll together. This is accomplished by ring 44 and a friction fit between a has 45 and socket 46.

Another important feature of the invention is that each core member 28 is tapered with its minimum cross-sectional area at its end 48 remote from the core faces 33 (except for the enlargements 49 which receive rivets 50). Such a configuration concentrates the magnetic field toward the front of the core members 28 at their pole faces 33 to provide the maximum effective magnetic field for the size of the coil. This configuration also moves the center of gravity of the core toward the front of the tool where it is grasped to facilitate easier handling; and minimizes the amount of iron used in the core, reducing weight and cost.

It can be seen that the positioning of the core and coil within the grasping portion of the casing, the positioning of the armature of the front of cavity 15, and the tapered configuration of the core members 28 all cooperate to provide a slender, wellbalanced and powerful tool while facilitating the use of a relatively small elongated coil 26.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and is herein described in detail one embodiment of the invention, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

I claim:

1. In an electric tool or the like, an electromagnet having a coil and an armature member mounted for movement toward and away from said coil, a core comprised of two pieces with said coil being disposed therebetween, at least one of said pieces having a portion extending into said coil, and a hinge member pivotally securing the two pieces of said core together at adjacent ends thereof, said hinge member including means for guiding said armature in its movement toward and away from said coil.

2. The electric tool of claim 1 including a movable portion of the tool mounted on the armature for vibratory movement toward and away from said core and wherein said hinge member includes means for guiding said movable portion of the tool in its vibratory movement.

3. In an electric tool or the like, an electromagnet having a coil and an armature member mounted for movement toward and away from said coil, a core comprised of two pieces for receiving said coil therebetween, the two pieces of said core being hinged together at adjacent ends thereof to permit the core pieces to be spread apart so that the coil may be positioned therebetween and the core pieces closed on the coil for assembly, and a casing having a cavity of a size to receive and hold the coil and core in assembled condition so that the coil and core assembly does not employ other fastening means to hold it together or to mount it in the casing.

4. The electric tool of claim 3 wherein at least one of said core pieces has a portion extending into said coil when said core pieces are closed on the coil.

5. The electric tool of claim 3 wherein said casing is a two part casing held together about said coil and core assembly by a ring member extending about the casing parts. 

1. In an electric tool or the like, an electromagnet having a coil and an armature member mounted for movement toward and away from said coil, a core comprised of two pieces with said coil being disposed therebetween, at least one of said pieces having a portion extending into said coil, and a hinge member pivotally securing the two pieces of said core together at adjacent ends thereof, said hinge member including means for guiding said armature in its movement toward and away from said coil.
 2. The electric tool of claim 1 including a movable portion of the tool mounted on the armature for vibratory movement toward and away from said core and wherein said hinge member includes means for guiding said movable portion of the tool in its vibratory movement.
 3. In an electric tool or the like, an electromagnet having a coil and an armature member mounted for movement toward and away from said coil, a core comprised of two pieces for receiving said coil therebetween, the two pieces of said core being hinged together at adjacent ends thereof to permit the core pieces to be spread apart so that the coil may be positioned therebetween and the core pieces closed on the coil for assembly, and a casing having a cavity of a size to receive and hold the coil and core in assembled condition so that the coil and core assembly does not employ other fastening means to hold it together or to mount it in the casing.
 4. The electric tool of claim 3 wherein at least one of said core pieces has a portion extending into said coil when said core pieces are closed on the coil.
 5. The electric tool of claim 3 wherein said casing is a two part casing held together about said coil and core assembly by a ring member extending about the casing parts. 